An important use thereof is as dressings, e.g. for the absorption of wound secretions for instance by coverage of ulcers and burns. A further important use is as prophylactic dressings for avoidance of blisters and wounds from shear and friction. Other important fields of use are as sealing pads for securing ostomy equipment such as ostomy bags, drains and/or collecting bags for drainage from surgical wounds and incontinence equipment. The dressings are also used with healing substances for wound care incorporated therein.
In the former case a rather heavy uptake of liquids takes place in the sealing pad because of the hydrocolloid therein, and sooner or later this will cause the sealing pad to loose its ability of sealing to the body of the patient. When used for fastening ostomy or drainage equipment the same will occur, first due to the uptake of sweat from the skin around the aperture of the sealing pad through which the stoma or drain protrudes into a collecting bag or similar device, and secondly because intestinal secretion or wound secretion may penetrate into the edges of the sealing pad around the aperture in question; it is hereby remarked that an important part of the function of such dressings when used as sealing pads for ostomy equipment is to tighten against the stoma in order to prevent aggressive (enzyme-containing) secretions from the artificial anus from entering into contact with the skin of the patient.
It is a well-known drawback in such dressings that the material constituting the sealing pad has a tendency to flow along the edges thereof, partly influenced by the absorbed aqueous secretions, but especially under the influence of pressure since the material of the sealing pad even at body temperature (approx. 37.degree. C.) is so plastic that even weak pressures for instance from folds of the skin will cause the substance to flow.
When the sealing pad material flows from under the cover layer, it will stick to garments or bed linen, which is unhygienic and is also inconvenient for the nursing staff.
In using such dressings in wound care it has therefore been usual to place a pressure sensitive tape, for instance a microporous tape, on the outer edges of the dressing and extending a suitable length, for instance 1-2 cm from the edge at all sides. This, however, is a price-raising measure and will also increase the time consumption of the nursing staff for bandaging. Also in ostomy equipment it is well-known, for instance from U.S. Pat. No. 4,213,458, corresponding to Danish Patent Specification No. 146,466, and from various commercial ostomy bags to provide ostomy sealing rings with a porous sheet material such as a microporous tape over and around the outer edge in order to prevent the material of the sealing pad from flowing out and to further strengthen the adhesion. This contributes to make the ostomy equipment in question more expensive and cannot be used on the inner part of the sealing pad adjacent the ostomy aperture.
It has been attempted to solve this problem by means of the dressing "DuoDERM".RTM. sold by the company ConvaTec, USA, in which the sealing pad only extends to a distance of about 1 cm from the edge of the water-tight cover layer, and which on the part thereof where the sealing pad is not present is provided with a thin layer of a pressure sensitive adhesive. A disadvantage of this construction is first that there is a sharp transition of thickness from the sealing pad to the pressure-sensitive adhesive, secondly that the latter is not water-absorbent which, i.a., involves the same inconvenience in the removal thereof as does the removal of ordinary plasters and thirdly that it is much more expensive to manufacture.
As the area of the skin to which the dressing or ostomy equipment is attached may often be very sensitive, the use of pressure sensitive adhesives that are not water absorbing should be avoided.